﻿<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright 2012 Eric Niebler

  Distributed under the Boost
  Software License, Version 1.0. (See accompanying
  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  -->
<header name="boost/proto/generate.hpp">
  <para>Contains definition of
    <computeroutput><classname alt="boost::proto::default_generator">proto::default_generator</classname></computeroutput>,
    <computeroutput><classname alt="boost::proto::generator">proto::generator</classname>&lt;&gt;</computeroutput>,
    <computeroutput><classname alt="boost::proto::pod_generator">proto::pod_generator</classname>&lt;&gt;</computeroutput>
    and other utilities that users can use to post-process new expression objects that
    Proto creates.</para>
  <namespace name="boost">
    <namespace name="proto">
      <!-- proto::default_generator -->
      <struct name="default_generator">
        <purpose>A simple generator that passes an expression through unchanged.</purpose>
        <description>
          <para>
            Generators are intended for use as the first template parameter to the
            <computeroutput><classname alt="proto::domain">proto::domain&lt;&gt;</classname></computeroutput>
            class template and control if and how expressions within that domain are to be customized.
            The <computeroutput>proto::default_generator</computeroutput> makes no modifications to the
            expressions passed to it.
          </para>
        </description>
        <inherit>
          <type><classname>proto::callable</classname></type>
        </inherit>
        <struct-specialization name="result">
          <template>
            <template-type-parameter name="This"/>
            <template-type-parameter name="Expr"/>
          </template>
          <specialization>
            <template-arg>This(Expr)</template-arg>
          </specialization>
          <typedef name="type">
            <type>Expr</type>
          </typedef>
        </struct-specialization>
        <method-group name="public member functions">
          <method name="operator()" cv="const">
            <type>Expr</type>
            <template>
              <template-type-parameter name="Expr"/>
            </template>
            <parameter name="expr">
              <paramtype>Expr const &amp;</paramtype>
              <description>
                <para>A Proto expression</para>
              </description>
            </parameter>
            <returns>
              <para><computeroutput>expr</computeroutput></para>
            </returns>
          </method>
        </method-group>
      </struct>

      <!-- proto::basic_default_generator -->
      <struct name="basic_default_generator">
        <purpose>
          A simple generator that passes an expression through unchanged while stating
          a preference for <classname>proto::basic_expr</classname>&lt;&gt; over
          <classname>proto::expr</classname>&lt;&gt;.</purpose>
        <inherit>
          <type><classname>proto::use_basic_expr</classname>&lt; <classname>proto::default_generator</classname> &gt;</type>
        </inherit>
      </struct>

      <!-- proto::generator -->
      <struct name="generator">
        <template>
          <template-nontype-parameter name="Extends">
            <type>template&lt; typename &gt; class</type>
          </template-nontype-parameter>
        </template>
        <purpose>A generator that wraps expressions passed to it in the specified extension wrapper.</purpose>
        <description>
          <para>
            Generators are intended for use as the first template parameter to the
            <computeroutput><classname alt="proto::domain">proto::domain&lt;&gt;</classname></computeroutput>
            class template and control if and how expressions within that domain are to be customized.
            <computeroutput>proto::generator&lt;&gt;</computeroutput> wraps each expression passed to it in
            the <computeroutput>Extends&lt;&gt;</computeroutput> wrapper.
          </para>
        </description>
        <struct-specialization name="result">
          <template>
            <template-type-parameter name="This"/>
            <template-type-parameter name="Expr"/>
          </template>
          <specialization>
            <template-arg>This(Expr)</template-arg>
          </specialization>
          <typedef name="type">
            <type>Extends&lt; Expr &gt;</type>
          </typedef>
        </struct-specialization>
        <method-group name="public member functions">
          <method name="operator()" cv="const">
            <type>Extends&lt; Expr &gt;</type>
            <template>
              <template-type-parameter name="Expr"/>
            </template>
            <parameter name="expr">
              <paramtype>Expr const &amp;</paramtype>
              <description>
                <para>A Proto expression</para>
              </description>
            </parameter>
            <returns>
              <para><computeroutput>Extends&lt;Expr&gt;(expr)</computeroutput></para>
            </returns>
          </method>
        </method-group>
      </struct>

      <!-- proto::pod_generator -->
      <struct name="pod_generator">
        <template>
          <template-nontype-parameter name="Extends">
            <type>template&lt; typename &gt; class</type>
          </template-nontype-parameter>
        </template>
        <purpose>A generator that wraps expressions passed to it in the specified extension wrapper and uses aggregate initialization for the wrapper. </purpose>
        <description>
          <para>
            Generators are intended for use as the first template parameter to the
            <computeroutput><classname alt="proto::domain">proto::domain&lt;&gt;</classname></computeroutput>
            class template and control if and how expressions within that domain are to be customized.
            <computeroutput>proto::pod_generator&lt;&gt;</computeroutput> wraps each expression passed
            to it in the <computeroutput>Extends&lt;&gt;</computeroutput> wrapper, and uses aggregate
            initialzation for the wrapped object.
          </para>
        </description>
        <inherit>
          <type><classname>proto::callable</classname></type>
        </inherit>
        <struct-specialization name="result">
          <template>
            <template-type-parameter name="This"/>
            <template-type-parameter name="Expr"/>
          </template>
          <specialization>
            <template-arg>This(Expr)</template-arg>
          </specialization>
          <typedef name="type">
            <type>Extends&lt; Expr &gt;</type>
          </typedef>
        </struct-specialization>
        <method-group name="public member functions">
          <method name="operator()" cv="const">
            <type>Extends&lt; Expr &gt;</type>
            <template>
              <template-type-parameter name="Expr"/>
            </template>
            <parameter name="expr">
              <paramtype>Expr const &amp;</paramtype>
              <description>
                <para>A Proto expression</para>
              </description>
            </parameter>
            <returns>
              <para>
                <computeroutput>Extends&lt;Expr&gt; that = {expr}; return that;</computeroutput>
              </para>
            </returns>
          </method>
        </method-group>
      </struct>

      <!-- by_value_generator -->
      <struct name="by_value_generator">
        <purpose>A generator that replaces child nodes held by reference with ones held by value.
          Use with <computeroutput><classname alt="proto::compose_generators">proto::compose_generators&lt;&gt;</classname>
          </computeroutput> to forward that result to another generator.
        </purpose>
        <description>
          <para>
            Generators are intended for use as the first template parameter to the
            <computeroutput><classname alt="proto::domain">proto::domain&lt;&gt;</classname></computeroutput>
            class template and control if and how expressions within that domain are to be customized.
            <computeroutput>proto::by_value_generator</computeroutput> ensures all child nodes are held
            by value. This generator is typically composed with a second generator for further processing,
            as <computeroutput><classname>proto::compose_generators</classname>&lt;proto::by_value_generator,
            MyGenerator&gt;</computeroutput>.
          </para>
        </description>
        <inherit>
          <type><classname>proto::callable</classname></type>
        </inherit>
        <struct-specialization name="result">
          <template>
            <template-type-parameter name="This"/>
            <template-type-parameter name="Expr"/>
          </template>
          <specialization>
            <template-arg>This(Expr)</template-arg>
          </specialization>
          <typedef name="type">
            <type><emphasis>unspecified</emphasis></type>
          </typedef>
        </struct-specialization>
        <method-group name="public member functions">
          <method name="operator()" cv="const">
            <type><emphasis>unspecified</emphasis></type>
            <template>
              <template-type-parameter name="Expr"/>
            </template>
            <parameter name="expr">
              <paramtype>Expr const &amp;</paramtype>
              <description>
                <para>A Proto expression.</para>
              </description>
            </parameter>
            <returns>
              <para>Equivalent to <computeroutput><functionname>proto::deep_copy</functionname>(expr)</computeroutput></para>
            </returns>
          </method>
        </method-group>
      </struct>

      <!-- proto::compose_generator -->
      <struct name="compose_generators">
        <template>
          <template-type-parameter name="First"/>
          <template-type-parameter name="Second"/>
        </template>
        <purpose>A composite generator that first applies one transform to an expression and then forwards
          the result on to another generator for further transformation.</purpose>
        <description>
          <para>
            Generators are intended for use as the first template parameter to the
            <computeroutput><classname alt="proto::domain">proto::domain&lt;&gt;</classname></computeroutput>
            class template and control if and how expressions within that domain are to be customized.
            <computeroutput>proto::compose_generators&lt;&gt;</computeroutput> is a composite generator
            that first applies one transform to an expression and then forwards the result on to another
            generator for further transformation.
          </para>
        </description>
        <inherit>
          <type><classname>proto::callable</classname></type>
        </inherit>
        <struct-specialization name="result">
          <template>
            <template-type-parameter name="This"/>
            <template-type-parameter name="Expr"/>
          </template>
          <specialization>
            <template-arg>This(Expr)</template-arg>
          </specialization>
          <inherit>
            <type>
    boost::result_of&lt;
      Second(typename boost::result_of&lt;First(Expr)&gt;::type)
    &gt;</type>
          </inherit>
        </struct-specialization>
        <method-group name="public member functions">
          <method name="operator()" cv="const">
            <type>typename boost::result_of&lt;
      Second(typename boost::result_of&lt;First(Expr)&gt;::type)
    &gt;::type</type>
            <template>
              <template-type-parameter name="Expr"/>
            </template>
            <parameter name="expr">
              <paramtype>Expr const &amp;</paramtype>
              <description>
                <para>A Proto expression.</para>
              </description>
            </parameter>
            <returns>
              <para><computeroutput>Second()(First()(expr))</computeroutput></para>
            </returns>
          </method>
        </method-group>
      </struct>

      <!-- proto::use_basic_expr -->
      <struct name="use_basic_expr">
        <template>
          <template-type-parameter name="Generator"/>
        </template>
        <inherit>
          <type>Generator</type>
        </inherit>
        <description>
          <para>
            Annotate a generator to indicate that it would
            prefer to be passed instances of
            <computeroutput><classname>proto::basic_expr</classname>&lt;&gt;</computeroutput> rather than
            <computeroutput><classname>proto::expr</classname>&lt;&gt;</computeroutput>.
          </para>
          <para>
            <computeroutput>use_basic_expr&lt; Generator &gt;</computeroutput> is itself a generator.
          </para>
        </description>
      </struct>

      <!-- proto::wants_basic_expr -->
      <struct name="wants_basic_expr">
        <template>
          <template-type-parameter name="Generator"/>
        </template>
        <inherit>
          <type>mpl::bool_&lt; <replaceable>true-or-false</replaceable> &gt;</type>
        </inherit>
        <description>
          <para>
            A Boolean metafunction that tests a generator to see whether
            it would prefer to be passed instances of
            <computeroutput><classname>proto::basic_expr</classname>&lt;&gt;</computeroutput> rather than
            <computeroutput><classname>proto::expr</classname>&lt;&gt;</computeroutput>.
          </para>
        </description>
      </struct>

    </namespace>
  </namespace>
</header>
